1. Field of the Invention
This invention relates to a three-dimensional confocal microscope and particularly to a three-dimensional confocal microscope for observing the three-dimensional shape of an observation target.
2. Description of the Related Art
By employing the Nipkow disk method that improves spatial resolution using a pinhole, a confocal microscope can condense light (laser beam) to a fine pinpoint illuminating the sample to be observed, and thus accurately measure one point in a three-dimensional space while eliminating redundant scattered light from the sample and poor focus. A confocal microscope of this type is described, for example, in JP-A-2002-72102.
With such a three-dimensional confocal microscope, it is possible to acquire slice images of individual layers of a sample without actually cutting the sample very thinly and to construct a precise three-dimensional image from the slice image data. Therefore, the confocal microscope is used for observation of physiological reactions and morphological observation of live cells in the fields of biology and biotechnology, or for surface observation of LSI devices in the semiconductor market.
FIG. 1 is a block diagram showing a conventional confocal microscope as described above. A confocal scanner 2 is attached to a camera port (not shown) of an optical microscope (hereinafter simply referred to as microscope) 3, and acquires a confocal image of a sample (not shown) after passing through the microscope 3, an actuator (for example, piezo-actuator) 4 and an objective lens 5. The image is picked up by a camera (for example, video rate camera) 1.
The video rate camera 1 outputs the picked-up image as a video signal 1a to the confocal scanner 2 and an image processing unit 6. The image processing unit 6 converts the video signal 1a to video data and stores the video data. On the other hand, the confocal scanner 2 performs rotational synchronization control of an internally installed Nipkow disk (not shown) in synchronization with the video signal 1a. 
The actuator 4 is driven by a scanning control signal 7a outputted from a controller 7 and scans the objective lens 5 in the direction of the optical axis. As the focal plane of the objective lens 5 is scanned in the direction of optical axis, consecutive confocal slice images of cross sections of the sample are acquired.
For the scanning of the objective lens 5 in the direction of optical axis, a Z-axis motor may be used instead of the actuator.
FIGS. 2A and 2B are schematic views showing shift of the focal plane due to expansion and contraction of the actuator 4. FIG. 2A shows a case where the actuator is expanded. FIG. 2B shows a case where the actuator is contracted.
However, since the conventional confocal microscope as described above uses moving units having moving parts such as actuator and motor, mechanical vibrations necessarily occur and such vibrations adversely affect the observation.
For example, when the frequency component of the vibration coincides with the eigen frequency of the microscope body, resonance occurs. This would lead to a problem that the surface of the sample becomes unstable and cannot be correctly observed.
Moreover, in the conventional confocal microscope, since the moving speeds of the moving units are low and the scanning speed on the focal plane of the objective lens is as low as a few Hz, a three-dimensional confocal laser microscope for high-speed scanning cannot be realized.